1. Field of the Invention
The present invention relates generally to optical control devices, and more particularly, to structures for optical control devices.
2. Description of the Related Art
Displacement detection based on optical technology is used in several applications, including optical input devices for computer systems. Data processing systems, or computer systems generally, are used in conjunction with a variety of input devices, such as, keyboards, pointing devices (e.g., mice, touchpads, and trackballs), joysticks, digital pens, and the like.
One example of optical displacement detection technology used in a pointing device is an optical mouse. Examples of pointing devices using optical detection technology and their operation are described in U.S. Pat. No. 5,288,993 to Bidiville, et al. (issued Feb. 22, 1994) entitled “Cursor Pointing Device Utilizing a Photodetector Array with Target Ball Having Randomly Distributed Speckles” and U.S. Pat. No. 5,703,356 to Bidiville, et al. (issued on Dec. 30, 1997) entitled “Pointing Device Utilizing a Photodetector Array,” the relevant portions of which are incorporated herein by reference.
There are significant advantages to using optical input devices over other types of input devices, such as, mechanical or opto-mechanical input devices. For example, mechanical or opto-mechanical input devices have mechanical components that are more susceptible to breakdown, wear, or clogging. Optical input devices reduce, and in some instances eliminate, a number of mechanical parts susceptible to these problems. Instead, optical input devices are manufactured with solid-state components that are less susceptible to such breakdown, dirt, or wear.
Optical displacement detection systems use differences in images captured over short periods of time to detect displacement and derive movement of a device relative to a surface. In general, a first image of a surface is captured at a first time and is compared with a second image captured shortly after the first image. The changes in the images over a small period of time correspond to displacement of the systems with respect to features of the surface. This displacement information is processed to derive movement data, such as, movement associated with a user display. For example, an optical pointing device in the form of a mouse captures images of a desk surface, and in the case of trackball, of a ball, providing displacement data of features on the surface that is processed to derive movement of a cursor in a computer screen.
A conventional optical displacement detection system, or optical system in general, includes a conventional illumination subsystem and a conventional optical sensor or detection subsystem. The conventional illumination subsystem includes a conventional illumination lens and a conventional source of electromagnetic energy or light source. Typically, the light source is a type of light emitting diode (LED). Generally, the light source is attached to a printed circuit board (PCB) and positioned with respect to the illumination lens to direct light through an opening on a bottom of the optical mouse onto an illumination spot on a surface (e.g., a desk).
The conventional sensor subsystem includes an imaging lens and a sensor. The sensor typically includes an image-capturing module, for example, one or more photosensor arrays. Some sensors also include controller circuitry associated with the image-capturing module, for example, in the form of digital circuits in the same die or device package. Generally, the controller circuitry performs digital signal processing (DSP) to derive movement data from the captured images. The sensor assembly is also typically mounted on the PCB and positioned so that the imaging lens optimally captures the electromagnetic energy (e.g., light) scattered from (or reflected off) the surface.
The sensor receives the scattered light from the imaged area through the opening at the bottom of the optical mouse. Thereafter, the sensor analyzes the images scanned or taken off the surface to provide displacement information. The imaged area substantially overlaps with the illumination so that the light is efficiently used to illuminate only that area of the surface that is imaged or scanned by the sensor.
As noted above, the solid state architecture of the conventional optical mouse allows for less structural wear and tear, which increases product life, while also allowing for relative ease of manufacturing, which decreases production costs. However, a conventional optical mouse may be susceptible to the entry of foreign elements into the housing through the opening at a bottom of the optical mouse. Examples of foreign elements include dust, liquids, and electrostatic discharge, all of which can damage components in the optical mouse. In turn, these foreign elements decrease reliability of the optical mouse, e.g., reducing photosensitivity, or causing the optical mouse to malfunction altogether, e.g., shorting the solid-state components.
Hence, there is a need for an optical mouse with a continuous or flush bottom (or base) that still provides characteristics of emitting light from the optical mouse while minimally impacting the intensity of the scattered light off of a surface back into the optical mouse.